Ingredients
Mains
- ¼ cup olive oil, plus more for greasing the pan
- 32 ounces baby Bella or crimini mushrooms, sliced
- 1 cup onions, chopped
- 2 teaspoons Diamond Crystal kosher salt (or 1 teaspoon other kosher salt)
- 1 tablespoon fresh garlic, minced
- ½ teaspoon black pepper
- ½ teaspoon dried thyme
- 1 cup Gruyere cheese, shredded
- 1 teaspoon dried parsley, for garnish
Instructions
- Preheat Oven and Prepare Baking Dish: Preheat your oven to 400°F (200°C). Grease a 2-quart baking dish with olive oil to prevent sticking and ensure easy cleanup.
- Sauté Mushrooms and Onions: Heat ¼ cup olive oil in a large, deep skillet over medium-high heat. Add the sliced mushrooms, chopped onions, and kosher salt. Cook while stirring occasionally until the mushrooms release their moisture and the liquid mostly evaporates, which should take about 10 minutes.
- Add Seasonings: Stir in the minced garlic, black pepper, and dried thyme. Continue cooking and stirring for one more minute to allow the flavors to meld. Then, remove the skillet from heat.
- Assemble the Casserole: Transfer the mushroom and onion mixture into the greased baking dish. Evenly sprinkle the shredded Gruyere cheese over the top.
- Bake: Place the baking dish in the preheated oven and bake until the casserole is hot and bubbly and the cheese has melted, about 15 minutes.
- Garnish and Serve: Remove from the oven and sprinkle with dried parsley for a fresh herby touch. Serve warm as a delicious side dish.
Notes
- Using fresh mushrooms provides the best texture and flavor.
- Gruyere cheese adds a nutty depth but Swiss or mozzarella can be substituted.
- Adjust salt to taste, especially if using a different type of salt.
- This casserole can be prepared ahead and baked just before serving for convenience.
- For a crispier top, broil for 1-2 minutes at the end of baking, watching carefully.
- Prep Time: 10 minutes
- Cook Time: 30 minutes
- Category: Side Dish
- Method: Baking
- Cuisine: American
